From sand to muck: Exploring belowground processes of managed dune and wetland ecosystems in New Jersey

This dissertation investigates belowground processes across New Jersey’s coastal ecosystems to better understand how plant-soil interactions influence restoration outcomes in anthropogenically modified coastal landscapes. Three concepts form the foundation of the hypotheses explored: first, that different plant species with contrasting root architectures and mycorrhizal associations contribute differently to substrate stabilization; second, that novel management approaches for invasive species may provide more selective control while minimizing non-target impacts; and third, that microbial communities in plant tissues respond to different control methods in ways that affect both immediate efficacy and subsequent decomposition dynamics.The research employed multiple methodological approaches across three primary studies. Chapter 2 examines woody plant contributions to sand stabilization in estuarine dune systems through field surveys at Cliffwood Beach and controlled greenhouse experiments using a novel planter box method to quantify sand retention. Results revealed compressed vegetation zonation in estuarine environments, with woody vegetation occurring approximately 30 meters from the water compared to 130-280 meters in oceanfront systems. Pinus rigida, with its ectomycorrhizal associations, developed significantly greater root biomass (10.69 ± 6.01 g) than Juniperus virginiana (6.64 ± 3.23 g) and showed higher hyphal colonization levels, along with moderately higher sand retention.Chapter 3 evaluates a novel bioherbicide for Phragmites australis control across contrasting wetland types. Field trials demonstrated significant reductions in P. australis coverage (>80%) at both freshwater and brackish sites, with site-specific conditions strongly influencing treatment effectiveness. Post-treatment plant community recovery varied dramatically between sites, with the brackish site supporting greater native plant diversity despite less complete initial P. australis control. Greenhouse experiments revealed that seeds remained viable when planted in bioherbicide-treated soils, compared with soil treated with a glyphosate-containing herbicide which caused complete inhibition. Additionally, native wetland plants treated with a foliar application of the bioherbicide did not show significantly reduced health, while the glyphosate-containing herbicide caused complete mortality of all treated plants. These greenhouse results suggest potential advantages for using the bioherbicide in sensitive ecosystems where further restoration is desired. Chapter 4 examines how different herbicide mechanisms affect bacterial endophyte communities in P. australis roots and rhizomes. Genomic analysis revealed distinct community shifts following treatment, with both herbicides increasing bacterial diversity compared to untreated controls though different taxonomic groups were driving the shifts in the plant tissues treated with bioherbicide versus the glyphosate-containing herbicide, suggesting that the differences were not due to plant death alone. The bioherbicide treatment particularly increased the abundance of Gammaproteobacteria and bacteria with cellulolytic capabilities, suggesting conditions that might support more rapid decomposition of persistent underground biomass.These findings demonstrate the importance of considering belowground processes in coastal ecosystem management. The research supports more function-oriented restoration approaches that recognize site-specific conditions and underscores the value of monitoring belowground responses to management interventions. Results suggest that incorporating appropriate woody species in estuarine dune restoration and considering both immediate and long-term effects of invasive species control methods could enhance coastal ecosystem resilience in the face of ongoing anthropogenic stressors.